Among the three thousand species of trees and bushes growing on what weather conditions permit in Poland, most are of foreign origin. Therefore, it is difficult to imagine how poor the variety of vegetation used to occur in Poland a few centuries ago. Despite the wide selection of species and varieties now possible for cultivation in Poland, it is still necessary to expand new representatives of foreign flora. We are looking for plants showing great resistance to pollution or possessing crown matching the narrow streets in cities. These are just some of the reasons for the introduction of new species and varieties, but the most important argument is the need to create an increasingly diversified areas of green.